The present invention relates to automatic transmissions.
In recent years, multiple speeds, for example, eight forward speeds, have been realized in automatic transmissions that are mounted in vehicles. At the same time, from the point of view of vehicle mounting characteristics, disposing many structural components, for example, clutches, compactly is required.
Conventionally, an automatic transmission has been proposed in which, for two clutches having one input member that is shared and the other that is different, one clutch that is disposed on the inner diameter side is fit in the clutch drum of the other clutch that is disposed on the outer diameter side, and the two clutches are aligned in parallel in the axial direction. A reduction in the size is thus realized in the axial direction (see, for example, Japanese Patent Application, JP-A-2006-342845).
The clutch drum of the one clutch that is disposed on the outer diameter side and the clutch drum of the other clutch that is disposed on the inner diameter side are spline engaged together in a rotational direction at a cylindrical boss portion that is formed at the inner diameter side thereof. The outer spline is formed on the outer circumference of the boss portion of the one clutch, and the inner spline is formed on the inner periphery of the boss portion of the other clutch.
In addition, the working oil chamber and a cancel oil chamber of the other clutch are provided on the boss portion of the one clutch on which the spline is formed, the hydraulic pressure (or oil) is supplied via oil holes that are provided in the boss portion of the other clutch, and the working oil chamber and the cancel oil chamber of the other clutch on the outer diameter side is structured by changing the position on the back side of the other clutch in the radial direction.